Rainfall calculator english units how much water falls during a storm.
1 inch of rain fall on a 1200sq foot roof.
Multiply the area of your roof by the amount of rainfall you wish to calculate for.
Multiplying that number by the local maximum rainfall intensity 6 8 inches per hour yields an adjusted.
It is the middle of july in georgia and both you and your tomatoes are wilting in your yard both looking to the sky and hoping for rain.
Use our metric system version.
That s 600 less gallons you have to pay for and use from your town water supply.
The 6 in 12 pitch factor 1 1 multiplied by 1 000 yields an effective area of 1 100 square feet.
For example a 4 12 pitch roof that is 100 square feet.
For example on a 2 000 square foot roof you can collect 2 000 x 0 56 1 120 gallons inch of rain.
6 inch 3 840 square feet.
If you have 1 000 square feet of roof on your house and it rains just 1 inch you can collect 600 gallons of water to be used in your garden for washing your car or just for drop irrigation around your property.
Total roof area also affects runoff.
An inch of rain is not much but it if falls in half an hour it could flood a gutter.
A roof that is 50 feet long by 20 feet wide for 34 inches of rainfall in a.
When you look at the numbers it s surprising how much water you can collect every time it rains.
The number of feet multiplied by 144 equals inches.
To get an idea how much water the roof of your own house might yield use the rainfall harvest calculator above.
A 30 foot long by 20 foot wide roof in a 1 inch rainfall but you can only collect from half of the roof length of roof feet x width of roof feet x 6gallons per square ft x 75 x inches of rainfall gallons of rainfall collected calculate for.
The pitch of the roof is the rise over a 12 inch run.
A house in chicago has a roof whose actual drainage area is 1 000 square feet.
Just a half inch of rain falling on a 1 000 square foot roof will yield 300 gallons of water.
So how can you do the math for your own roof.
For example if you have a roof that measures 1 500 square feet that equals 216 000 square inches.
Roof pitch area multipliers.
5 inch 2 500 square feet.
The total rainfall and how rapidly it falls will affect the runoff from the roof.
In this example 600 x 240 x 1 144 000 cubic inches of water divide by 231 to get the number of gallons because 1 gallon 231 cubic inches.
Pitch or steepness also is a factor.
So a 50 x 20 roof is 600 x 240 multiply the roof dimensions by the number of inches of rainfall.
Take the dimensions of the footprint of your roof and convert them to inches.
If your average rainfall was 25 inches year your annual collection potential is 1 120 x 25 28 000 gallons year.
1 500 x 144 216 000 multiply those 216 000 square inches by the rainfall.
Rain barrel supplies list.
To find how much rain you can collect in an average rain year multiply this number by the average inches of rain.
Next multiply the footprint of the roof by the multiplier below for your roof pitch to find the overall roof area.